1. Field of the Invention
The present invention relates to a display device, and in particular, to a liquid crystal display (LCD) device.
2. Description of the Related Art
An LCD is not a self-emissive light element but instead is a light receiving element necessitating an independent light source, and has a technical limitation in terms of brightness, contrast, angle of visual field, magnification of the view, etc. Therefore, efforts have been actively made to develop a novel flat display device. An example is research into an organic electroluminescent (EL) device that has merits such as operability with low voltage, self-emission of light, a compact and slim appearance, wide angle of visual field and a quick response.
The EL of an organic material was first discovered in single crystal Anthracene. Nevertheless, the first discovery failed to develop the EL device for more than the next 20 years due to its size limit and difficulty in growing the single crystal, as well as to an extremely high voltage (˜1000V) required for its operation. Recently, however, a device has been developed having a film thickness of only 1000 Å and operable with a low voltage of about 10V.
An organic light emitting diode (OLED) comprises a cathode layer, an organic film layer, and an anode layer. The organic film layer comprises an electron transport layer, a hole transport layer, and an organic emitting layer. If necessary, an electron injection layer and a hole injection layer may be additionally comprised of the organic film layer.
An inorganic EL device is similar to a compound in its concept that a fluorescent material is emitted by electric energy. However, a slight difference lies in terms of the excitation, which is a core of the emitting mechanism. In the inorganic EL device, light emission is caused by energy generated by an acceleration and collision of electrons due to high voltage. In the organic EL device, however, light emission is caused by rebinding of the holes injected from an anode and a cathode with electrons.
The following is a detailed description of a conventional LCD made with reference to FIG. 1.
FIG. 1 is a sectional view of a conventional LCD illustrating a structure thereof.
Referring to FIG. 1, the conventional LCD comprises two insulating substrates 101, 101a facing each other and having liquid crystal sealed therebetween, color filter layers 102 of red, green and blue formed on the upper substrate 101 for expressing colors, and black matrices 103 for shielding penetration of light into the parts other than the pixel electrodes formed on the lower substrate 101a. 
A common electrode 105 is formed to cover the color filter layers 102 and the black matrices. It is possible to form an overcoat 104 before forming the common electrode 105.
Thin film transistors consisting of a gate electrode 106 elongated from a gate line, a source electrode 107 and a drain electrode 108 elongated from a data line, which is arrayed to cross the gate line, are formed on the lower substrate 101a at regular intervals. A pixel electrode is connected to the drain electrode 108 through a contact hole. A backlight 112 is provided on an outer surface of the lower substrate 101a. 
Spacers 109 are dispersed between the color filter layers and thin film transistors to maintain a cell gap.
However, the conventional LCD and its fabrication method pose the following problems.
An LCD is not a self-emissive light element but a light receiving element necessitating an independent light source, thereby requiring a backlight. The electric power consumed by the backlight occupies a dominant part of the electric power supplied to the LCD. Further, the backlight becomes a bar to reducing weight, thickness, length and size of the LCD.